Phase 3 PR 19 — LDAP user identity + Basic256Sha256 security profile. Replaces the anonymous-only endpoint with a configurable security profile and an LDAP-backed UserName token validator. New IUserAuthenticator abstraction in Backend/Security/: LdapUserAuthenticator binds to the configured directory (reuses the pattern from Admin.Security.LdapAuthService without the cross-app dependency — Novell.Directory.Ldap.NETStandard 3.6.0 package ref added to Server alongside the existing OPCFoundation packages) and maps group membership to OPC UA roles via LdapOptions.GroupToRole (case-insensitive). DenyAllUserAuthenticator is the default when Ldap.Enabled=false so UserName token attempts return a clean BadUserAccessDenied rather than hanging on a localhost:3893 bind attempt. OpcUaSecurityProfile enum + LdapOptions nested record on OpcUaServerOptions. Profile=None keeps the PR 17 shape (SecurityPolicies.None + Anonymous token only) so existing integration tests stay green; Profile=Basic256Sha256SignAndEncrypt adds a second ServerSecurityPolicy (Basic256Sha256 + SignAndEncrypt) to the collection and, when Ldap.Enabled=true, adds a UserName token policy scoped to SecurityPolicies.Basic256Sha256 only — passwords must ride an encrypted channel, the stack rejects UserName over None. OtOpcUaServer.OnServerStarted hooks SessionManager.ImpersonateUser: AnonymousIdentityToken passes through; UserNameIdentityToken delegates to IUserAuthenticator.AuthenticateAsync — rejected identities throw ServiceResultException(BadUserAccessDenied); accepted identities get a RoleBasedIdentity that carries the resolved roles through session.Identity so future PRs can gate writes by role. OpcUaApplicationHost + OtOpcUaServer constructors take IUserAuthenticator as a dependency. Program.cs binds the new OpcUaServer:Ldap section from appsettings (Enabled defaults false, GroupToRole parsed as Dictionary<string,string>), registers IUserAuthenticator as LdapUserAuthenticator when enabled or DenyAllUserAuthenticator otherwise. PR 17 integration test updated to pass DenyAllUserAuthenticator so it keeps exercising the anonymous-only path unchanged. Tests — SecurityConfigurationTests (new, 13 cases): DenyAllAuthenticator rejects every credential; LdapAuthenticator rejects blank creds without hitting the server; rejects when Enabled=false; rejects plaintext when both UseTls=false AND AllowInsecureLdap=false (safety guard matching the Admin service); EscapeLdapFilter theory (4 rows: plain passthrough, parens/asterisk/backslash → hex escape) — regression guard against LDAP injection; ExtractOuSegment theory (3 rows: finds ou=, returns null when absent, handles multiple ou segments by returning first); ExtractFirstRdnValue theory (3 rows: strips cn= prefix, handles single-segment DN, returns plain string unchanged when no =). OpcUaServerOptions_default_is_anonymous_only asserts the default posture preserves PR 17 behavior. InternalsVisibleTo('ZB.MOM.WW.OtOpcUa.Server.Tests') added to Server csproj so ExtractOuSegment and siblings are reachable from the tests. Full solution: 0 errors, 180 tests pass (8 Core + 14 Proxy + 24 Configuration + 6 Shared + 91 Galaxy.Host + 19 Server (17 unit + 2 integration) + 18 Admin). Live-LDAP integration test (connect via Basic256Sha256 endpoint with a real user from GLAuth, assert the session.Identity carries the mapped role) is deferred to a follow-up — it requires the GLAuth dev instance to be running at localhost:3893 which is dev-machine-specific, and the test harness for that also needs a fresh client-side certificate provisioned by the live server's trusted store.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.OtOpcUa.Server/OpcUa/OpcUaApplicationHost.cs

@@ -3,6 +3,7 @@ using Opc.Ua;
 using Opc.Ua.Configuration;
 using ZB.MOM.WW.OtOpcUa.Core.Hosting;
 using ZB.MOM.WW.OtOpcUa.Core.OpcUa;
+using ZB.MOM.WW.OtOpcUa.Server.Security;
 
 namespace ZB.MOM.WW.OtOpcUa.Server.OpcUa;
 
@@ -18,6 +19,7 @@ public sealed class OpcUaApplicationHost : IAsyncDisposable
 {
     private readonly OpcUaServerOptions _options;
     private readonly DriverHost _driverHost;
+    private readonly IUserAuthenticator _authenticator;
     private readonly ILoggerFactory _loggerFactory;
     private readonly ILogger<OpcUaApplicationHost> _logger;
     private ApplicationInstance? _application;
@@ -25,10 +27,11 @@ public sealed class OpcUaApplicationHost : IAsyncDisposable
     private bool _disposed;
 
     public OpcUaApplicationHost(OpcUaServerOptions options, DriverHost driverHost,
-        ILoggerFactory loggerFactory, ILogger<OpcUaApplicationHost> logger)
+        IUserAuthenticator authenticator, ILoggerFactory loggerFactory, ILogger<OpcUaApplicationHost> logger)
     {
         _options = options;
         _driverHost = driverHost;
+        _authenticator = authenticator;
         _loggerFactory = loggerFactory;
         _logger = logger;
     }
@@ -55,7 +58,7 @@ public sealed class OpcUaApplicationHost : IAsyncDisposable
             throw new InvalidOperationException(
                 $"OPC UA application certificate could not be validated or created in {_options.PkiStoreRoot}");
 
-        _server = new OtOpcUaServer(_driverHost, _loggerFactory);
+        _server = new OtOpcUaServer(_driverHost, _authenticator, _loggerFactory);
         await _application.Start(_server).ConfigureAwait(false);
 
         _logger.LogInformation("OPC UA server started — endpoint={Endpoint} driverCount={Count}",
@@ -126,22 +129,8 @@ public sealed class OpcUaApplicationHost : IAsyncDisposable
             ServerConfiguration = new ServerConfiguration
             {
                 BaseAddresses = new StringCollection { _options.EndpointUrl },
-                SecurityPolicies = new ServerSecurityPolicyCollection
-                {
-                    new ServerSecurityPolicy
-                    {
-                        SecurityMode = MessageSecurityMode.None,
-                        SecurityPolicyUri = SecurityPolicies.None,
-                    },
-                },
-                UserTokenPolicies = new UserTokenPolicyCollection
-                {
-                    new UserTokenPolicy(UserTokenType.Anonymous)
-                    {
-                        PolicyId = "Anonymous",
-                        SecurityPolicyUri = SecurityPolicies.None,
-                    },
-                },
+                SecurityPolicies = BuildSecurityPolicies(),
+                UserTokenPolicies = BuildUserTokenPolicies(),
                 MinRequestThreadCount = 5,
                 MaxRequestThreadCount = 100,
                 MaxQueuedRequestCount = 200,
@@ -164,6 +153,58 @@ public sealed class OpcUaApplicationHost : IAsyncDisposable
         return cfg;
     }
 
+    private ServerSecurityPolicyCollection BuildSecurityPolicies()
+    {
+        var policies = new ServerSecurityPolicyCollection
+        {
+            // Keep the None policy present so legacy clients can discover + browse. Locked-down
+            // deployments remove this by setting Ldap.Enabled=true + dropping None here; left in
+            // for PR 19 so the PR 17 test harness continues to pass unchanged.
+            new ServerSecurityPolicy
+            {
+                SecurityMode = MessageSecurityMode.None,
+                SecurityPolicyUri = SecurityPolicies.None,
+            },
+        };
+
+        if (_options.SecurityProfile == OpcUaSecurityProfile.Basic256Sha256SignAndEncrypt)
+        {
+            policies.Add(new ServerSecurityPolicy
+            {
+                SecurityMode = MessageSecurityMode.SignAndEncrypt,
+                SecurityPolicyUri = SecurityPolicies.Basic256Sha256,
+            });
+        }
+
+        return policies;
+    }
+
+    private UserTokenPolicyCollection BuildUserTokenPolicies()
+    {
+        var tokens = new UserTokenPolicyCollection
+        {
+            new UserTokenPolicy(UserTokenType.Anonymous)
+            {
+                PolicyId = "Anonymous",
+                SecurityPolicyUri = SecurityPolicies.None,
+            },
+        };
+
+        if (_options.SecurityProfile == OpcUaSecurityProfile.Basic256Sha256SignAndEncrypt
+            && _options.Ldap.Enabled)
+        {
+            tokens.Add(new UserTokenPolicy(UserTokenType.UserName)
+            {
+                PolicyId = "UserName",
+                // Passwords must ride an encrypted channel — scope this token to Basic256Sha256
+                // so the stack rejects any attempt to send UserName over the None endpoint.
+                SecurityPolicyUri = SecurityPolicies.Basic256Sha256,
+            });
+        }
+
+        return tokens;
+    }
+
     public async ValueTask DisposeAsync()
     {
         if (_disposed) return;

src/ZB.MOM.WW.OtOpcUa.Server/OpcUa/OpcUaServerOptions.cs

@@ -1,5 +1,23 @@
+using ZB.MOM.WW.OtOpcUa.Server.Security;
+
 namespace ZB.MOM.WW.OtOpcUa.Server.OpcUa;
 
+/// <summary>
+///     OPC UA transport security profile selector. Controls which <c>ServerSecurityPolicy</c>
+///     entries the endpoint advertises + which token types the <c>UserTokenPolicies</c> permits.
+/// </summary>
+public enum OpcUaSecurityProfile
+{
+    /// <summary>Anonymous only on <c>SecurityPolicies.None</c> — dev-only, no signing or encryption.</summary>
+    None,
+
+    /// <summary>
+    ///     <c>Basic256Sha256 SignAndEncrypt</c> with <c>UserName</c> and <c>Anonymous</c> token
+    ///     policies. Clients must present a valid application certificate + user credentials.
+    /// </summary>
+    Basic256Sha256SignAndEncrypt,
+}
+
 /// <summary>
 ///     OPC UA server endpoint + application-identity configuration. Bound from the
 ///     <c>OpcUaServer</c> section of <c>appsettings.json</c>. PR 17 minimum-viable scope: no LDAP,
@@ -39,4 +57,18 @@ public sealed class OpcUaServerOptions
     ///     Admin UI.
     /// </summary>
     public bool AutoAcceptUntrustedClientCertificates { get; init; } = true;
+
+    /// <summary>
+    ///     Security profile advertised on the endpoint. Default <see cref="OpcUaSecurityProfile.None"/>
+    ///     preserves the PR 17 endpoint shape; set to <see cref="OpcUaSecurityProfile.Basic256Sha256SignAndEncrypt"/>
+    ///     for production deployments with LDAP-backed UserName auth.
+    /// </summary>
+    public OpcUaSecurityProfile SecurityProfile { get; init; } = OpcUaSecurityProfile.None;
+
+    /// <summary>
+    ///     LDAP binding for UserName token validation. Only consulted when the active
+    ///     <see cref="SecurityProfile"/> advertises a UserName token policy. When
+    ///     <c>LdapOptions.Enabled = false</c>, UserName token attempts are rejected.
+    /// </summary>
+    public LdapOptions Ldap { get; init; } = new();
 }

src/ZB.MOM.WW.OtOpcUa.Server/OpcUa/OtOpcUaServer.cs

@@ -5,6 +5,7 @@ using Opc.Ua.Server;
 using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 using ZB.MOM.WW.OtOpcUa.Core.Hosting;
 using ZB.MOM.WW.OtOpcUa.Core.OpcUa;
+using ZB.MOM.WW.OtOpcUa.Server.Security;
 
 namespace ZB.MOM.WW.OtOpcUa.Server.OpcUa;
 
@@ -17,12 +18,14 @@ namespace ZB.MOM.WW.OtOpcUa.Server.OpcUa;
 public sealed class OtOpcUaServer : StandardServer
 {
     private readonly DriverHost _driverHost;
+    private readonly IUserAuthenticator _authenticator;
     private readonly ILoggerFactory _loggerFactory;
     private readonly List<DriverNodeManager> _driverNodeManagers = new();
 
-    public OtOpcUaServer(DriverHost driverHost, ILoggerFactory loggerFactory)
+    public OtOpcUaServer(DriverHost driverHost, IUserAuthenticator authenticator, ILoggerFactory loggerFactory)
     {
         _driverHost = driverHost;
+        _authenticator = authenticator;
         _loggerFactory = loggerFactory;
     }
 
@@ -50,6 +53,63 @@ public sealed class OtOpcUaServer : StandardServer
         return new MasterNodeManager(server, configuration, null, _driverNodeManagers.ToArray());
     }
 
+    protected override void OnServerStarted(IServerInternal server)
+    {
+        base.OnServerStarted(server);
+        // Hook UserName / Anonymous token validation here. Anonymous passes through; UserName
+        // is validated against the IUserAuthenticator (LDAP in production). Rejected identities
+        // throw ServiceResultException which the stack translates to Bad_IdentityTokenInvalid.
+        server.SessionManager.ImpersonateUser += OnImpersonateUser;
+    }
+
+    private void OnImpersonateUser(Session session, ImpersonateEventArgs args)
+    {
+        switch (args.NewIdentity)
+        {
+            case AnonymousIdentityToken:
+                args.Identity = new UserIdentity(); // anonymous
+                return;
+
+            case UserNameIdentityToken user:
+            {
+                var result = _authenticator.AuthenticateAsync(
+                    user.UserName, user.DecryptedPassword, CancellationToken.None)
+                    .GetAwaiter().GetResult();
+                if (!result.Success)
+                {
+                    throw ServiceResultException.Create(
+                        StatusCodes.BadUserAccessDenied,
+                        "Invalid username or password ({0})", result.Error ?? "no detail");
+                }
+                args.Identity = new RoleBasedIdentity(user.UserName, result.DisplayName, result.Roles);
+                return;
+            }
+
+            default:
+                throw ServiceResultException.Create(
+                    StatusCodes.BadIdentityTokenInvalid,
+                    "Unsupported user identity token type: {0}", args.NewIdentity?.GetType().Name ?? "null");
+        }
+    }
+
+    /// <summary>
+    ///     Tiny UserIdentity carrier that preserves the resolved roles so downstream node
+    ///     managers can gate writes by role via <c>session.Identity</c>. Anonymous identity still
+    ///     uses the stack's default.
+    /// </summary>
+    private sealed class RoleBasedIdentity : UserIdentity
+    {
+        public IReadOnlyList<string> Roles { get; }
+        public string? Display { get; }
+
+        public RoleBasedIdentity(string userName, string? displayName, IReadOnlyList<string> roles)
+            : base(userName, "")
+        {
+            Display = displayName;
+            Roles = roles;
+        }
+    }
+
     protected override ServerProperties LoadServerProperties() => new()
     {
         ManufacturerName = "OtOpcUa",